Mechanical design and force control algorithm for a robot leg with hydraulic series-elastic actuators

Abstract

This article presents a mechanical design structure for hydraulic actuators using the principle of series-elastic actuator, considering the restriction of mechanical structure, weight and size, as well as the requirement of high joint torques due to the large payload. An articulated leg was designed to incorporate with two of these elastic elements symmetrically for each joint. Further, for the hydraulic system with a position servo loop, a force control algorithm was particularly proposed and developed for joint torque tracking and Cartesian impedance control. Finally, a number of experiments were carried out on the leg platform, and the experimental results validated the effectiveness of the force control algorithm and the performance of the overall system.

Fixed‐time asymmetric barrier Lyapunov function‐based model‐free hybrid position/force control for 3‐DOF SEA‐based manipulator with output constraints

“…, applying the proposed FBMHC ( 16)-( 18), for the parameters satisfying p ≥ 𝜎 ≥ 𝛾 1 , 𝛾 2 = 𝛾 1 + 𝜀 > 0, 𝛾 3 = 𝛾 2 + 𝜀 ≥ 0, 𝜀 < 0 and 𝜂 > 0 are constant numbers, then it follows that z 1 converges in finite time and satisfies the inequality (7).…”

“…6 A PI-type impedance control is used to control its output torque and position for the SEA-based robot leg. 7 For the SEA-based single-link manipulator, an impedance controller based on singular perturbation theory and time delay estimation technology is proposed. 8 An iterative learning impedance controller is proposed for the SEA-based rehabilitation robot, 9 which iteratively realizes the required impedance model and adapts to the repetitive nature of patient tasks during the treatment process.…”

“…The impedance control can effectively adjust the relationship between position and interaction force for SEA‐based manipulators 6 . A PI‐type impedance control is used to control its output torque and position for the SEA‐based robot leg 7 . For the SEA‐based single‐link manipulator, an impedance controller based on singular perturbation theory and time delay estimation technology is proposed 8 .…”

Improvement of Torque Estimation for Series Viscoelastic Actuator Based on Dual Extended Kalman Filter

“…The reliable way to acquire output torque of SVA by motor current is to perform the calculation when angular acceleration equals to zero. In such a situation, the dynamic model of SVA can be simplified as Equation (2) in which the inertial term is out of consideration.…”

“…Thanks to its relative low output impedance and convenience of torque measurement, series elastic actuators (SEA) are commonly used in the field of robot joint force control in recent years [1][2][3]. The metal springs used in SEA exhibit linear relationships between output force and position, which greatly increases torque control accuracy owing to the ability of turning the force control problem into a position control problem [4].…”